Field of the Invention
The present invention relates to an apparatus and a process for producing a honeycomb body having a multiplicity of passages which are permeable to a fluid, in particular a catalyst carrier body.
Catalyst carrier bodies are used to eliminate pollutants, in particular in motor vehicle exhaust gases. Such catalyst carrier bodies may involve metallic honeycomb bodies. The honeycomb body includes a stack having a multiplicity of at least partially structured sheet metal layers. The stack is twisted in opposite directions about itself and about a central region. Such a structural configuration for a honeycomb body is known, for example, from U.S. Pat. No. 4,923,109.
International Patent Publication WO 90/03220, corresponding to U.S. Pat. Nos. 5,139,844; 5,105,539 and 5,135,794, discloses a metallic catalyst carrier body for motor vehicles, which is composed of at least partially structured sheet metal layers. That catalyst carrier body includes at least three stacks of sheet metal layers, wherein at least three of the stacks are each folded about a respectively associated bend line in the central region of the honeycomb body and in the folded condition are twisted in the same direction about each other and about the central region with the bend lines.
Known apparatuses for producing such catalyst carrier bodies include a fork-shaped wrapping or winding device which is rotatable about an axis and which engages each stack, as well as former segments which close to constitute a former. The inside contour of the closed former corresponds to the outside contour of the honeycomb body in the wrapped or wound condition. The most frequent shape in which the honeycomb body is produced is cylindrical. In order to ensure that the stacks are wound around themselves and around a central region, the former segments are moved towards the stack in such a way that, during the rotary movement of the forked twisting device, the stack or stacks bear against the edge of the former segments and that edge forms a support device. Towards the end of the production procedure the former is completely closed and thus imparts the definitive form to the honeycomb body.
The known apparatuses have two former segments which are movable towards each other and away from each other in a straight line. During the closing operation there is a danger of at least one of the former segments moving in the opposite direction to the direction of movement of a portion of a stack which is still to be twisted. If the former segment encounters the portion of the stack, that can give rise to undesired deformation of the stack or stacks. That deformation has the result of causing individual sheet metal layers to be partially buckled. As a result the structure of the finished honeycomb body is adversely affected. On one hand the strength of the honeycomb body suffers as a result and on the other hand there is a local variation in the passage cross-sections.